Method of grinding thin-film magnetic heads using optical grinding markers

Abstract

According to the present grinding method, a plurality of optical markers are formed by photolithography such that the markers are embedded in a chiplet having a magnetic head. Markers are preferably in the shape of a bar having predetermined height, width and length and are spaced from each other by a predetermined distance where one end of the bars are sequentially offset from each other by a predetermined amount. During coarse grinding of the magnetic head as the magnetic head surface material is ground away, the end-face of the bars, one at a time, become visible. The closer the grinding surface approaches the desired inductive throat or MR element height, more end-faces become visible. Coarse grinding continues until a predetermined number of end-faces become visible at which point the grinding process is terminated and the magnetic head is ready for the final lapping process.

We claim: 
     
       1. In a chiplet comprising a thin-film magnetic head and an optical marker, said chiplet having a ground surface, said optical marker for detecting the amount of grinding performed on said magnetic head, said optical marker comprising: a block having a lapping surface, the lapping surface being adjacent to said chiplet ground surface; and   a plurality of gaps formed within said block such that as the lapping surface of said block is ground away, the block breaks into individual solid bars, each solid bar having an end-face where visual counting of the number of end-faces indicate the amount of the grinding left to be performed to reach a desired grinding target.   
     
     
       2. An optical marker as recited in claim 1 wherein said bars are separated from each other by a known distance to provide visual resolution. 
     
     
       3. An optical marker as recited in claim 2 wherein said separation distance is in the range of about 5 to 25 microns. 
     
     
       4. An optical marker as recited in claim 1 wherein the lapping surface of said block is substantially parallel to the ground surface. 
     
     
       5. An optical marker as recited in claim 1 wherein said optical marker is made of electrically conducting material. 
     
     
       6. An optical marker as recited in claim 5 wherein said electrically conducting material is copper. 
     
     
       7. An optical marker as recited in claim 1 wherein said optical marker is made of insulating material. 
     
     
       8. An optical marker as recited in claim 7 wherein said insulating material is silicon dioxide. 
     
     
       9. An optical marker as recited in claim 7 wherein said insulating material is aluminum dioxide. 
     
     
       10. An optical marker as recited in claim 1 wherein said optical marker is made of magnetic material. 
     
     
       11. An optical marker as recited in claim 10 wherein said magnetic material is permalloy. 
     
     
       12. An optical marker as recited in claim 10 wherein said magnetic material is sendust. 
     
     
       13. In a chiplet comprising a thin-film magnetic head and a pair of optical markers, said chiplet comprising a ground surface, said optical markers for detecting the amount of skew present in a magnetic head grinding process, one optical marker formed on each opposite side of the head adjacent to the ground surface, each optical marker comprising: a block, said block having a lapping surface adjacent to the ground surface of said chiplet; and   a plurality of gaps formed within said block such that as the lapping surface of the block is ground away, the block breaks into individual solid bars, each solid bar having an end-face where visual counting of the number of end-faces appearing on opposite sides of the head visually indicate the degree of skew present in the grinding process.   
     
     
       14. An optical marker as recited in claim 13 wherein said optical marker is made of electrically conducting material. 
     
     
       15. An optical marker as recited in claim 14 wherein said electrically conducting material is copper. 
     
     
       16. An optical marker as recited in claim 13 wherein said optical marker is made of insulating material. 
     
     
       17. An optical marker as recited in claim 16 wherein said insulating material is silicon dioxide. 
     
     
       18. An optical marker as recited in claim 16 wherein said insulating material is aluminum dioxide. 
     
     
       19. An optical marker as recited in claim 13 wherein said optical marker is made of magnetic material. 
     
     
       20. An optical marker as recited in claim 19 wherein said magnetic material is permalloy. 
     
     
       21. An optical marker as recited in claim 19 wherein said magnetic material is sendust. 
     
     
       22. In a chiplet comprising a thin-film magnetic head and an optical marker, said chiplet having a ground surface, said optical marker for detecting the amount of grinding left to be performed on said magnetic head, said optical marker comprising: a block having a lapping surface adjacent to the ground surface of said chiplet; and   a plurality of gaps formed within said block where each gap is bounded at one end by a surface of an end-wall such that as the lapping surface of the block is ground away, the block breaks into individual solid bars, each solid bar having an end-face such that visual counting of the number of end-faces appearing on the lapping surface indicate the amount of grinding left to be performed to reach a desired grinding target.   
     
     
       23. An optical marker as recited in claim 22 wherein the surface of said end-walls are sequentially offset from each other by a predetermined amount. 
     
     
       24. An optical marker as recited in claim 23 wherein said offset is in the range of about 1 to 10 microns. 
     
     
       25. An optical marker as recited in claim 22 wherein said bars are separated from each other by a known distance sufficiently large enough to provide visual resolution. 
     
     
       26. An optical marker as recited in claim 22 wherein said optical marker is made of electrically conducting material. 
     
     
       27. An optical grinding marker as recited in claim 22 wherein said optical marker is made of insulating material. 
     
     
       28. An optical grinding marker as recited in claim 22 wherein said optical marker is made of magnetic material.